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    A refined finite element method for stress analysis of rotors and rotating disks with variable thickness

    , Article Acta Mechanica ; Volume 228, Issue 2 , 2017 , Pages 575-594 ; 00015970 (ISSN) Entezari, A ; Kouchakzadeh, M. A ; Carrera, E ; Filippi, M ; Sharif University of Technology
    Springer-Verlag Wien  2017
    In this paper, a refined finite element method (FEM) based on the Carrera unified formulation (CUF) is extended for stress analysis of rotors and rotating disks with variable thickness. The variational form of the 3D equilibrium equations is obtained using the principle of minimum potential energy and solved by this method. Employing the 1D CUF, a rotor is assumed to be a beam along its axis. In this case, the geometry of the rotor can be discretized into a finite number of 1D beam elements along its axis, while the Lagrange polynomial expansions may be employed to approximate the displacement field over the cross section of the beam. Therefore, the FEM matrices and vectors can be written in... 

    On the security of O-PSI a delegated private set intersection on outsourced datasets

    , Article 2017 14th International ISC (Iranian Society of Cryptology) Conference on Information Security and Cryptology, ISCISC 2017 ; 2018 , Pages 77-81 ; 9781538665602 (ISBN) Mahdavi Oliaee, M ; Delavar, M ; Ameri, M. H ; Mohajeri, J ; Aref, M. R ; Sharif University of Technology
    In recent years, determining the common information privately and efficiently between two mutually mistrusting parties have become an important issue in social networks. Many Private set intersection (PSI) protocols have been introduced to address this issue. By applying these protocols, two parties can compute the intersection between their sets without disclosing any information about components that are not in the intersection. Due to the broad range of computational resources that the cloud can provide for its users, determining the set intersection by cloud may decrease the computational cost of the users. The proposed protocol by Abadi et al. is one of the introduced protocols in this... 

    Online signature verification using I-vector representation

    , Article IET Biometrics ; Volume 7, Issue 5 , 2018 , Pages 405-414 ; 20474938 (ISSN) Zeinali, H ; BabaAli, B ; Hadian, H ; Sharif University of Technology
    Institution of Engineering and Technology  2018
    Signature verification (SV) is one of the common methods for identity verification in banking, where for security reasons, it is very important to have an accurate method for automatic SV (ASV). ASV is usually addressed by comparing the test signature with the enrolment signature(s) signed by the individual whose identity is claimed in two manners: online and offline. In this study, a new method based on the i-vector is proposed for online SV. In the proposed method, a fixed-length vector, called i-vector, is extracted from each signature and then this vector is used for template making. Several techniques such as nuisance attribute projection (NAP) and within-class covariance normalisation... 

    3D dynamic coupled thermoelastic solution for constant thickness disks using refined 1D finite element models

    , Article Applied Mathematical Modelling ; Volume 60 , 2018 , Pages 273-285 ; 0307904X (ISSN) Entezari, A ; Filippi, M ; Carrera, E ; Kouchakzadeh, M. A ; Sharif University of Technology
    Elsevier Inc  2018
    This paper deals with the generalized coupled thermoelastic solution for disks with constant thickness. It is a sequel to the authors's previous work in which refined 1D Galerkin finite element models with 3D-like accuracies are developed for theories of coupled thermoelasticity. Use of the reduced models with low computational costs may be of interest in a laborious time history analysis of the dynamic problems. In this paper, the developed models are applied and evaluated for a 3D solution of the dynamic generalized coupled thermoelasticity problem in the disk subjected to thermal shock loads. Comparison of the obtained result with the results available in the literature verified the... 

    A bridge between dual porosity and multiscale models of heterogeneous deformable porous media

    , Article International Journal for Numerical and Analytical Methods in Geomechanics ; 2018 ; 03639061 (ISSN) Hajiabadi, M. R ; Khoei, A. R ; Sharif University of Technology
    John Wiley and Sons Ltd  2018
    In this paper, a multiscale homogenization approach is developed for fully coupled saturated porous media to represent the idealized sugar cube model, which is generally employed in fractured porous media on the basis of dual porosity models. In this manner, an extended version of the Hill-Mandel theory that incorporates the microdynamic effects into the multiscale analysis is presented, and the concept of the deformable dual porosity model is demonstrated. Numerical simulations are performed employing the multiscale analysis and dual porosity model, and the results are compared with the direct numerical simulation through 2 numerical examples. Finally, a combined multiscale-dual porosity... 

    Sparse decomposition of two dimensional signals

    , Article 2009 IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP 2009, Taipei, 19 April 2009 through 24 April 2009 ; 2009 , Pages 3157-3160 ; 15206149 (ISSN); 9781424423545 (ISBN) Ghaffari, A ; Babaie Zadeh, M ; Jutten, C ; Institute of Electrical and Electronics Engineers; Signal Processing Society ; Sharif University of Technology
    In this paper, we consider sparse decomposition (SD) of two-dimensional (2D) signals on overcomplete dictionaries with separable atoms. Although, this problem can be solved by converting it to the SD of one-dimensional (1D) signals, this approach requires a tremendous amount of memory and computational cost. Moreover, the uniqueness constraint obtained by this approach is too restricted. Then in the paper, we present an algorithm to be used directly for sparse decomposition of 2D signals on dictionaries with separable atoms. Moreover, we will state another uniqueness constraint for this class of decomposition. Our algorithm is obtained by modifying the Smoothed L0 (SL0) algorithm, and hence... 

    Task scheduling mechanisms in cloud computing: A systematic review

    , Article International Journal of Communication Systems ; Volume 33, Issue 6 , 2020 Amini Motlagh, A ; Movaghar, A ; Rahmani, A. M ; Sharif University of Technology
    John Wiley and Sons Ltd  2020
    Today, cloud computing has developed as one of the important emergent technologies in communication and Internet. It offers on demand, pay per use access to infrastructure, platforms, and applications. Due to the increase in its popularity, the huge number of requests need to be handled in an efficient manner. Task scheduling as one of the challenges in the cloud computing supports the requests for assigning a particular resource so as to perform effectively. In the resource management, task scheduling is performed where there is the dependency between tasks. Many approaches and case studies have been developed for the scheduling of these tasks. Up to now, a systematic literature review... 

    Investigation of the continuum-rarefied flow and isotope separation using a hybrid CFD-DSMC simulation for UF6 in a gas centrifuge

    , Article Annals of Nuclear Energy ; 2020 Ghazanfari, V ; Akbar Salehi, A ; Reza Keshtkar, A ; Mahdi Shadman, M ; Hossein Askari, M ; Sharif University of Technology
    Elsevier Ltd  2020
    UF6 gas flow in the total regions of a rotor with the radius of 0.1 m and the length of 1 m in axisymmetric and steady states was simulated using a new hybrid CFD-DSMC method in the OpenFOAM framework. Implicit coupled density-based scheme was performed for CFD method, and Variable Hard Sphere (VHS) and diffuse model were employed in DSMC method. Also, as an initial estimation, the local Knudsen number was applied to determine the interface location between the continuum-rarefied regions (r = 0.0855 m). Then it was modified (r = 0.084 m) to reduce the computational cost. The comparison results of pure CFD and CFD-DSMC methods illustrated that there were large differences between the flow... 

    Dual-diffusivity stochastic model for macromolecule release from a hydrogel

    , Article ACS Applied Bio Materials ; Volume 3, Issue 7 , 2020 , Pages 4208-4219 Jahanmir, G ; Lau, C. M. L ; Abdekhodaie, M. J ; Chau, Y ; Sharif University of Technology
    American Chemical Society  2020
    A three-dimensional model has been developed to describe the multiphase release of macromolecular drugs encapsulated in a hydrogel. The heterogeneity of network mesh size was considered by assigning varying diffusion coefficients to the network lattices randomly. Using a stochastic approach, the random nature of diffusion of drug molecules was captured within the network. The simplest form of distribution containing two diffusion coefficients was tested. To generate the drug release profiles for experimental validation under the limitation of computational cost, a simple scaling relationship was employed. Unlike the single-diffusivity model, the dual-diffusivity model showed good agreement... 

    An identity based authentication protocol for smart grid environment using physical uncloneable function

    , Article IEEE Transactions on Smart Grid ; Volume 12, Issue 5 , 2021 , Pages 4426-4434 ; 19493053 (ISSN) Sanaullah Badar, H. M ; Qadri, S ; Shamshad, S ; Faizan Ayub, M ; Mahmood, K ; Kumar, N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Smart grid plays an important role in managing demand response management in modern smart city using Information and Communication Technologies (ICTs). In smart grid environment, sensors are widely used for surveillance. These are deployed on the high tension power supply lines which help to share the information to control center about line breakage or any other flaw. Besides the cyber-attacks, sensors may also experience physical attacks as they are deployed on high-tension power lines in an open environment. Moreover, an attacker can also impersonate the information exchanged between sensors, gateways and control centers. Therefore, the most indispensable requirement is to prevent these... 

    Neutron noise simulator based on the boundary element method (BEM)

    , Article Annals of Nuclear Energy ; Volume 159 , 2021 ; 03064549 (ISSN) Hosseini, S. A ; Mohamadbeygi, S ; Sharif University of Technology
    Elsevier Ltd  2021
    The purpose of the present study is to develop the neutron diffusion solver and neutron noise simulator based on the Boundary Element Method (BEM). The 2-D, 2-G neutron/adjoint diffusion equation and corresponding neutron/adjoint noise equation were solved using the mentioned method. The developed neutron static and noise simulator based on the finite element method gives accurate results when the more number of the elements is used. The motivation of the present research is to use the boundary element method to reduce the computational cost. The boundary element method attempts to use the given boundary conditions to fit boundary values into the integral equation, rather than values... 

    Seismic performance assessment of eccentrically braced steel frames with energy-absorbing links under sequential earthquakes

    , Article Journal of Building Engineering ; Volume 33 , 2021 ; 23527102 (ISSN) Mohsenian, V ; Filizadeh, R ; Hajirasouliha, I ; Garcia, R ; Sharif University of Technology
    Elsevier Ltd  2021
    Recent studies have indicated the need of considering aftershocks in the seismic design/assessment of structures. This article investigates the effect of sequential mainshock and aftershock earthquakes on eccentrically braced steel frames with vertical energy-absorbing links. To achieve this, 4, 8 and 12-storey frame buildings are modelled in Perform3D® software considering non-linear behaviour of materials and components. The frames are subjected to a set of 12 main earthquake records corresponding to the required hazard level, and then subsequent aftershocks are applied using incremental dynamic analysis (IDA). To reduce the computational cost, an alternative approach is also adopted by... 

    GIM: GPU accelerated RIS-Based influence maximization algorithm

    , Article IEEE Transactions on Parallel and Distributed Systems ; Volume 32, Issue 10 , 2021 , Pages 2386-2399 ; 10459219 (ISSN) Shahrouz, S ; Salehkaleybar, S ; Hashemi, M ; Sharif University of Technology
    IEEE Computer Society  2021
    Given a social network modeled as a weighted graph GG, the influence maximization problem seeks kk vertices to become initially influenced, to maximize the expected number of influenced nodes under a particular diffusion model. The influence maximization problem has been proven to be NP-hard, and most proposed solutions to the problem are approximate greedy algorithms, which can guarantee a tunable approximation ratio for their results with respect to the optimal solution. The state-of-the-art algorithms are based on Reverse Influence Sampling (RIS) technique, which can offer both computational efficiency and non-trivial (1-1/e-ϵ)-approximation ratio guarantee for any epsilon >0ϵ>0.... 

    Assessment of offshore structures under extreme wave conditions by Modified Endurance Wave Analysis

    , Article Marine Structures ; Volume 39 , December , 2014 , Pages 50-69 ; ISSN: 09518339 Dastan Diznab, M. A ; Mohajernassab, S ; Seif, M. S ; Tabeshpour, M. R ; Mehdigholi, H ; Sharif University of Technology
    Recently, various approaches have been introduced to estimate the response of offshore structures in different sea states by stepwisely intensifying records. In this article, a more practical approach entitled Modified Endurance Wave Analysis (MEWA) considering the random and probabilistic nature of wave loading and utilizing optimal time duration is introduced. Generation procedure of this approach is described based on two practical wave theories: random and constrained new-wave. In addition, assessment of a simplified model representing a typical fixed offshore platform under extreme wave conditions in the Persian Gulf is performed making use of MEWA. A comparative analysis has been also... 

    A successive boundary element model for investigation of sloshing frequencies in axisymmetric multi baffled containers

    , Article Engineering Analysis with Boundary Elements ; Volume 37, Issue 2 , 2013 , Pages 383-392 ; 09557997 (ISSN) Ebrahimian, M ; Noorian, M. A ; Haddadpour, H ; Sharif University of Technology
    This study presents a developed successive Boundary Element Method to determine the symmetric and antisymmetric sloshing natural frequencies and mode shapes for multi baffled axisymmetric containers with arbitrary geometries. The developed fluid model is based on the Laplace equation and Green's theorem. The governing equations of fluid dynamic and free surface boundary condition are also applied to proposed model. A zoning method is presented to model arbitrary arrangement of baffles in multi baffled axisymmetric tanks. The influence of each zone on neighboring zones is applied by introducing interface influence matrix which correlates the velocity potential of interfaces to their flux. By... 

    AQM controller design for TCP networks based on a new control strategy

    , Article Telecommunication Systems ; Volume 57, Issue 4 , December , 2013 , Pages 295-311 ; 10184864 (ISSN) Kahe, G ; Jahangir, A. H ; Ebrahimi, B ; Sharif University of Technology
    Kluwer Academic Publishers  2013
    When the network suffers from congestion, the core or edge routers signal the incidence of congestion through the active queue management (AQM) to the sources. The time-varying nature of the network dynamics and the complex process of retuning the current AQM algorithms for different operating points necessitate the development of a new AQM algorithm. Since the non-minimum phase characteristics of the network dynamics restrict direct application of the proportional-integral-derivative (PID) controller, we propose a compensated PID controller based on a new control strategy addressing the phase-lag and restrictions caused by the delay. Based on the unstable internal dynamics caused by the... 

    A new approach for multi-source data prediction in wireless sensor networks: Collaborative filtering

    , Article 2012 International Conference on Wireless Communications and Signal Processing, WCSP 2012 ; 2012 ; 9781467358293 (ISBN) Inanloo, M ; Ashouri, M ; Gheibi, S ; Hemmatyar, A. M. A ; Sharif University of Technology
    The prime shortcoming of Wireless Sensor Networks (WSNs) is their energy constraint. The main energy consumer in a sensor node is its radio transmitter. One of the most effective methods to reduce the data transmission rate is data prediction. By data prediction, the amount of transmitted data is reduced; which results in energy saving and the longevity of the network life. Environmental variations almost have similar effects on different sensor sources in a sensor device. So, considering the correlation between different sources reduces the noise impact and increases data prediction accuracy. In this paper, temporal and multi-source correlations are used, to reduce data transmission in... 

    Thermomechanical behaviours of strip and work-rolls in cold rolling process

    , Article Journal of Strain Analysis for Engineering Design ; Volume 46, Issue 8 , June , 2011 , Pages 794-804 ; 03093247 (ISSN) Koohbor, B ; Serajzadeh, S ; Sharif University of Technology
    A finite element analysis was developed to determine thermomechanical behaviours of strip and work-roll during cold rolling process under practical rolling conditions. The velocity field was first obtained using a rigid-plastic finite element formulation and then it was used to assess the strain and stress distributions within the strip and at the same time, a thermal finite element model based on streamline upwind Petrov-Galerkin scheme was employed to predict temperature distribution within the metal being rolled. In the next stage, the predicted temperature and stress fields at the contact region of strip/work-roll were employed as the boundary conditions to evaluate the thermomechanical... 

    Porous media approach in thermohydraulic analysis of high temperature reactors in pressurized/depressurized cooldown: An improvement

    , Article Progress in Nuclear Energy ; Volume 80 , 2015 , Pages 119-127 ; 01491970 (ISSN) Nouri Borujerdi, A ; Tabatabai Ghomsheh, S. I ; Sharif University of Technology
    Elsevier Ltd  2015
    The current study aims at introducing a 2D and fast-running code for the issues pertinent to design, analysis and safety in modular high temperature reactors. While the porous media approach is only applied to pebble bed type, the analysis in this paper covers both pebble bed and prismatic reactor. A time-dependent mass equation along with energy conservation equation for the cooling gas and a time-dependent energy conservation equation for the solid was solved. Appropriate series of constitutive equations (e.g. heat transfer coefficient, effective heat conductivity of solid, heat transfer coefficient, pressure drop etc.) has been recruited as well. In addition a finite-volume method is... 

    The control of a thermal system with large time delay using of LQG and lead-compensator

    , Article 2010 IEEE International Conference on Mechatronics and Automation, ICMA 2010, 4 August 2010 through 7 August 2010 ; August , 2010 , Pages 1842-1847 ; 9781424451418 (ISBN) Zareh, S. H ; Jahromi, A. F ; Abbasi, M ; Khayyat, A. A ; Sharif University of Technology
    This paper will first describe the Linear-Quadratic-Gaussian (LQG) and Lead-Compensator when the Proportional-Integral-Derivative (PID) controllers are inactive for procedures that have large delay time (LDT) in transfer stage. Therefore in those states, LQG and Lead Compensator perform better than the PID controllers. The constrained LQG is optimal and stabilizing. The solution algorithm is guaranteed to terminate in finite time with a computational cost that has a reasonable upper bound compared to the minimal cost for computing the optimal solution. In this work all actual working area condition for instance noises and disturbances are considered. Eventually, LQG and Lead Compensator have...